In my last column I talked about the Rainbow Trout’s ability to see colour and how colour changed based on light penetration into the water. I thought I would discuss the trout’s other senses, as they depend upon all their senses to locate a food source, with sight being their primary receptor.
I know when I was a youngster, the first thing I was told was not to make noise when I went fishing. At first, I thought this was a way to keep me from talking too much, but after I share the following information with you, the bigger picture should emerge. To begin with, sound and vibrations can be sensed by the trout and can augment vision in low light and murky water. Their two ears are designed to give them an excellent sense of hearing, allowing them the ability to better home in on prey or flee from unusual noises. Accordingly, the larger fish have larger swim bladders, which aid in amplifying sound waves in the water. Their lateral line also picks up vibrations in the water at a frequency not picked up by their ears alone.
Aquatic invertebrates create vibrations in the water that trout can detect at close range with their lateral line allowing them to identify a given food source. This same lateral line helps the trout determine the size of an organism as well. The same sensor allows the fish, when it is small, to detect the presence of a predator in the water.
Several years ago, while fishing with Brian Smith, a fellow member of the 100 Mile Fly Fishers on Sheridan Lake, I was shocked at how well fish can detect sounds, and how fast these sounds move through the water. We were anchored in about 35 feet of water, targeting fish as they came onto the screen of my sonar. At one point, I saw a fish on the sounder, and as I moved my rod, it tapped against the motor. The fish disappeared off the screen before I could even utter an obscenity. Lesson learned! I never in my wildest dreams imagined the fish could react that quickly to a sound travelling down my line to the fly.
I have had other experiences watching fish in shallow water reacting to unusual sounds like dropping an object onto the floor of my boat, even though I always have carpet on the aluminium floor to deaden sounds.
There are certain lures and flies an angler can use to help the fish key in on them. Certain spinners set up a vibration in the water, as do flies with palmered hackles or large hackles. Knowing this may give one angler an edge over another. Other lures are also designed to attract fish through their movement in the water as well.
Knowing what I know now, I make every effort to minimize noises by soundproofing my boat, avoiding banging my anchors or oars against the side of the boat, and holding my rod away from the gunwale or motor.
Have fun out there and know that increased knowledge will help you enjoy your day on the water. Remember to be safe and legal!
My last column, discussing colour changes in water, didn’t have the associated chart with it in the paper due to limited space, raising some questions. The online version did have it, nonetheless. I am hoping to include it here in this column for those who didn’t see it.
